1. Field of Invention
The present invention relates to a bioreactor system and method for treating wastewater, and more particularly to a wastewater treatment system and method utilizing a membrane bioreactor.
2. Discussion of Related Art
Biological treatment of wastewater is widely practiced. Wastewater is commonly treated with waste activated sludge, in which biological solids are acted upon by bacteria during a sludge residence time within a treatment tank. However, biological treatment produces unwanted waste sludge which must be appropriately disposed of. Waste sludge is commonly removed from the system and sent off-site for incineration or disposal in landfills.
Moreover, any organics present in the wastewater are acted upon by the bacteria only during a hydraulic retention time within a treatment tank. Because the hydraulic retention time is generally less than the sludge residence time, organics and recalcitrant organics in particular, may not be treated or destroyed. As a result, there are certain organic compounds that can pass through a treatment process unchanged to be discharged in either an effluent or residual sludge.
Powdered activated carbon is used in enhanced biological treatment processes allowing the organics to remain within the treatment tank for the hydraulic retention time and the sludge residence time to undergo both adsorptive and biological treatments. However, because both biological growth and adsorption of organic components occurs, wasting of excess solids is required. In addition, the powdered activated carbon is lost from the treatment process with the removal of biosolids and must, therefore, be continually replaced.